Efficient XMPP user search

Question

I want to efficiently check for all local address book contacts if they have a jabber account. The users are registered on the XMPP server with the mobile phone number. I currently send the following XEP-0055 stanza to the ejabberd server and evaluate the result.

<iq type="set" id="searchByUserName" to="vjud.ecoimac1.local" from="[e-mail]">
  <query xmlns="jabber:iq:search">
    <x xmlns="jabber:x:data" type="submit">
      <field type="hidden" var="FORM_TYPE">
        <value>jabber:iq:search</value>
      </field>
      <field var="user">
        <value>[phone]</value>
      </field>
    </x>
  </query>
</iq>

This works but is not efficient. For each number a query has to be sent. Other apps like WhatsApp do the same job. Is there a more efficient way?

Answer 1

I have now following efficient solution:

On server side I did set up a MySQL database backend for eJabberd and on the web server a PHP interface provides a user lookup for the client application. The app sends a HTTP POST request with a set of jabber user names to check. The PHP script looks up which users are registered and returns a response containing the indices of the registered users.

<?php

// HTTP POST sent from client app
// Do authentication here...

// Read all parameters
$users = array();
$user = $_POST["username0"];
for ($i = 1; !empty($user); $i++)
{
    // Add user
    $users[] = $user;

    // Next parameter
    $user = $_POST["username".$i];
}
if (empty($users))
{
    echo "Success"; // nothing to do
    exit;
}

// Create mySQL connection
$db = mysqli_connect("localhost", "user", "password", "database");
if (!$db)
{
    $descr = mysqli_connect_error();
    echo "Error: ".$descr;
    exit;
}

// Prepare query
// SELECT username FROM users WHERE username IN ('[phone]','[phone]',...)
$query = "SELECT username FROM users WHERE username IN(";
foreach ($users as $user)
{
    $query .= "'".$user."',";
}
$query = rtrim($query, ",");
$query .= ")";

// Execute query and generate result
$result = "Success";
$recset = mysqli_query($db, $query); // [[phone],[phone],...]
while ($rec = mysqli_fetch_object($recset))
{
    $index = find_user($rec->username, $users);
    if ($index >= 0)
    {
        $result .= "\t".$index;
    }
}

echo $result;

function find_user($username, $users)
{
    for ($idx = 0; $idx < count($users); $idx++)
    {
        if ($users[$idx] == $username)
        {
            return $idx; // found at index
        }
    }
    return -1; // not found
}

?>